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Exercises: Bromination and fluorination of alkanes

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Exercise

Why are the radical fluorination and iodination of alkanes not very useful reactions?

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Fluorination is very endothermic, which means that the reaction rate is also very low.

Iodination is a very endothermic reaction, which means that it virtually never occurs.

Fluorination is very exothermic and can, therefore, hardly be controlled. In addition, the selectivity regarding the various types of C-H bonds is very low.

Iodination is very exothermic can, therefore, hardly be controlled. In addition, the selectivity regarding the variuos types of C-H bonds is very low.

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Exercise

Which postulate can be used to explain the higher selectivity of the bromination compared to the chlorination?

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The Hammock postulate.

The Hammond postulate.

The Half-moon postulate.

The Hamborn postulate.

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Exercise

Which of the following statements are correct?

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In the chlorination of 2-methylpropane, in the two possible transition states, the C-H and H-Cl bonds are approximately equally strong. Therefore, the radical character is differently distributed among the carbon and chlorine atom.

In the transition states of the bromination of 2-methylpropane, the radical character is located mainly at the carbon atom.

The transition state of the bromination resembles the products, while the transition state of the chlorination resembles the starting products.

The transition states of the abstraction of a hydrogen atom from an alkane by either a chlorine or bromine radical are considerably different.

The transition state of the chlorination resembles the product, while the transition state of the bromination resembles the starting products.

In the radical bromination of 2-methylpropane, the bromine radical, that is less reactive than a chlorine radical, generates the tertiary alkyl radical much more easily than the primary alykl radical.

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Exercise

What does the reactivity-selectivity-principle declare?

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The higher the selectivity of a reagent is, the more reactive it is as well.

The less reactive a reagent is, the lower its selectivity is, as well.

The more reactive a reagent is, the less selective it is as well.

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